Customers shop BJ's like a supermarket, and it reflects an advantage Costco should be worried about

Costco, Sam's Club, and BJ's are the three biggest warehouse club chains in the United States. These stores offer paying members discounts on items bought in bulk.

The nature of these stores means that members are less likely to make frequent trips there.

BJ's, however, has a larger fresh-food section than its rivals and offers a wider selection of smaller items, which analysts say drives more frequent visits to its stores.

America's three biggest warehouse chains — Costco, BJ's, and Sam's Club — all operate around the same general concept: to provide lower prices to members by selling items in bulk.

The very nature of their business means that customers don't need to come here for weekly visits. These aren't your average grocery stores and, most likely, you don't need to buy a box containing 30 bags of chips or a five-pound bag of coffee every week. These stores are designed to serve the customer who wants to stock on up on non-perishable items and make monthly or fortnightly visits to the store.

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10 Kirkland items you should always buy at Costco

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10 Kirkland items you should always buy at Costco

Almonds

Health experts can’t stop raving about the benefits of nuts, but man, are they expensive—and Costco agrees. The warehouse store reportedly stopped selling other brands almost entirely when they couldn’t justify how high their prices had gotten. Now you can get a massive three-pound bag of Kirkland Signature almonds for just $13, which isn’t much more than you’d normally pay for a Blue Diamond bag almost half its size. Stock up on these other 15 foods nutritionists always buy at Costco.

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Bacon

When Consumer Reports put different bacon brands to the test several years ago, Kirkland Signature soared above the rest, thanks to its crispy texture and smoky-sweet flavor—which is even more impressive considering its low price. Make room in the freezer, because this bulk buy is no joke: Four pounds for $13.69. Plus, learn the secrets behind Costco’s famous $4.99 rotisserie chicken.

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Liquor

Across the board, Costco’s value-sized bottles of booze get rave reviews. Its vodka in particular has garnered a cult following, with rumors swirling that it shares the same water source as Grey Goose. The luxury vodka brand denies those claims, but that’s not necessarily a bad thing—the cheap Kirkland version actually outshines Grey Goose in taste tests. Just $25 for 1.75 liters of high-quality liquor? Can’t beat that.

No matter how tasty they are, it can be hard to justify the price of pistachios—unless you’re at Costco. At face value, a $15 bag seems like a lot, but you’ll change your mind when you see the three-pound package you get. For comparison, a two-pound bag of Wonderful pistachios costs $13 on Amazon. Really, you can’t go wrong with any Kirkland nuts, so stock up on walnuts and mixed nuts too.

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Plastic wrap

Kirkland’s food wrap gets high marks for its durability, so the low price is just the icing on the cake. Paying less than $10 for two 750-square-foot rolls, you won’t need to stock up on plastic wrap again for a long time. You should also always stock up if you see this symbol on a Costco price tag.

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Quinoa

With more protein and fiber than white rice, quinoa has unsurprisingly gone from food fad to kitchen staple. Unfortunately, that hasn’t convinced most companies to lower their prices. At Target, you’ll get three pounds for $12 (not bad), but Costco offers 4.5 pounds for $9. It’s still not as cheap as rice, but it’s definitely a healthier option.

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Extra Virgin Olive Oil

A 2010 report found that most EVOO on U.S. store shelves wasn’t extra virgin like their labels claimed. One notable exception: Kirkland’s organic version. So not only are you paying less per serving than you would at the supermarket, but you can guarantee good quality. How’s that for a solid deal?

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Cheese

If you think everything tastes better when covered in cheese, Costco is the place to be. From goat cheese and Brie to Parmesan and Pecorino Romano, its cheeses are cheesemonger-quality with warehouse prices. The value-sized hunks of cheese might be excessive for a dinner for two, but Kirkland should be your go-to if you’re planning a party. Just steer clear of these things you should never buy at Costco.

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Baby formula

When you have an infant in tow, the last thing you want to worry about is overpriced baby formula. The FDA has strict nutrition requirements for baby formula, and Costco’s version is no exception. The non-GMO Kirkland baby formula’s ingredient list is nearly identical to Similac Advance’s, but it costs about half as much per ounce. Make sure you know these 15 secrets Costco employees won’t tell you.

BJ's, however, is closing the gap somewhat between a grocery store and a warehouse store. This predominantly East Coast-based chain offers more fresh food and non-bulk items than its competitors.

According to a recent note from Nomura, its fresh food section accounts for 27% of its sales. At Costco, for comparison, this department accounts for 16% of sales.

A larger selection of fresh or perishable food and smaller items drives more traffic to its stores. Around 20% of BJ's members make weekly visits, the Nomura analysts wrote.

Once in the store, these members are also more likely to make other purchases.

The three warehouse clubs use a similar tactic with their gas stations. As gas purchases tend to be recurring, having gas stations attached to stores is an effective way to drive foot traffic and encourage members to visit the store when they fill up their car's tank. It's also a way to attract members and keep existing ones loyal.